The present invention relates to a motion controller for a motor-driven transportation truck or trolley designed for an accompanying operator who controls it by means of a steering pole.
An accompanied transportation truck or trolley with steering pole is known, for example, from DE 12 39 573. The steering pole is pivoted around a horizontal axis attached to a steering frame and can be swivelled between a vertical position, in which the brake is simultaneously operated by means of an appropriate device, and a lower position--displaced through a vertical angle with respect to the first--in which the vehicle becomes capable of being steered and operated. An appropriate control unit arranged at the free end of the steering pole is provided for the travel and loading operations. It comprises, among others, a travel switch or controller such that the direction in which it is moved determines the direction of travel, while the distance through which it is moved simultaneously determines the traveling speed of the truck or trolley.
It is also known from DE 27 51 333 that the steering pole can be arranged at the upper end of a steering shaft that, passing through the housing of the driving unit, extends vertically downwards to a frame or support for the steering wheel, which in most cases is also driven by a motor. In connection with steering poles of this type it is also known that they can be swivelled through a certain distance about a horizontal axis, so that, with the help of the pole, the truck or trolley can also be steered and operated from a (driving) position on the vehicle itself.
DE 27 54 102 made known a steering pole for such accompanied low-slung truck or trolleys that is designed in such a way that the pole can be shortened without any substantial reduction of its resistance and with the control unit remaining at substantially the same level, where the extent of the shortening may correspond to the entire length of the pole. This arrangement excludes that the operator, when swivelling the control unit inwards, i.e. in the direction of the truck or trolley, will flip the pole upwards into a position in which the safety switch becomes laid bare or that the control unit at the end of the pole is swivelled through such a distance that the lever of the safety switch is swivelled out of its contact position.
DE 38 32 581 revealed a steering pole. for this type of truck or trolley in which traveling direction and speed switches are arranged in the control unit, together with a safety switch, the later on the front face. When the free end of the pole comes up against some resistance, which may also be due to its coming into contact with the operator, the emergency safety switch will immediately bring the brake into action, so that the operator cannot be run over by the vehicle.
From DE 37 16 375 there is known a motor-driven truck or trolley steered by means of a pole in which this pole, for the purpose of controlling the motor, is fitted with a switch-operating device that may be actuated in any arbitrary manner, the said device being situated in the vicinity of the handle at the end of the pole. For this purpose the handle, together with the end of the pole, may be arranged in such a manner as to permit it to be displaced with respect to the rest of the pole, complete with an appropriate device to sense the direction of the displacement and thus determine (set) the direction of motion of the vehicle. This arrangement is intended to make sure that whenever the pole is either picked up from its lowered position or lowered from its raised position, the various components that control the vehicle drive will not be inadvertently actuated when the operator gets hold of the handle and thus set the truck or trolley in motion.
The present invention sets out to solve the problem of a motion controller for a motor-driven transportation truck or trolley with steering pole that will give the accompanying operator a "direct" feeling for the vehicle without the distracting need for operating a motion switch.
The invention is based on the insight that the rotation path of a motion switch of the type normally used changes as a function of the swivel path of the steering pole. When operating the vehicle, the operator must always transform the desired vehicle performance into a rotary motion of his own hand. This becomes a disadvantage in particularly critical situations when the operator, rather than actuating the motion switch and reversing the direction of motion, tries to brake the rolling vehicle by either "holding" it or "pushing" it away.
The solution in accordance with the present invention comprises a sensor means that will produce a signal as a function of both the direction of the tractive force applied to the steering pole, i.e. push or pull, and the magnitude of that force, through a feed back controller unit that will set the direction of rotation and the speed of the motor driving the vehicle in accordance with the said signal.
When the steering pole of the accompanied vehicle is designed in accordance with the present invention, it becomes possible to convey to the operator a feeling similar to the one associated with a pole-steered truck or trolley devoid of a driving motor. The sensor means determines the pulling and/or pushing forces that the operator exerts on the steering pole and transforms them into a setting signal suitable for the motion controller. The feed back controller unit evaluates both the direction and the strength of the signal and then sends appropriately amplified signals to the driving motor. The invention thus creates a feed back controller unit that can be designed in such a way so as to make it possible to regulate tensile and compressive forces as a function of the load, the force and the speed at an ergonomically "comfortable" level.
With a view to preventing stumbling and the operator being run over by the vehicle, the maximum speed of such low-slung truck or trolleys is limited by [German] law to 6 km/hr. As previously mentioned, it is therefore known that an emergency switch can be fitted to the steering pole that will prevent the operator becoming trapped between an obstacle and the vehicle. The motion controller in accordance with the present invention does not require a separate emergency switch, because--for example--a rearward motion of the truck or trolley against the operator will cause the sensor means to reverse the direction of motion and prevent the operator being run over.
There are many possible ways in which the sensor means can be applied. In accordance with one version of the invention, one of these consists of using it to determine the force acting between the steering pole and the truck or trolley.
One version of the said sensor means is provided with a guide way that will cause it to respond only to tensile or compressive forces acting in the longitudinal direction of the steering pole and permit displacements only within this guide way, displacements that act proportionally on a signal transmitter (potentiometer, DMS, Hall sensor, etc.) This signal transmitter then sends a signal proportional to the tensile or compressive force to the feed back controller unit. The feed back controller unit then sets or regulates the motor in accordance with the direction and magnitude of the signal, so that the vehicle can reduce the pulling or pushing force exerted by the operator. We thus have a closed loop regulator circuit.
The properties of the regulator circuit can be realized either mechanically in the sensor or electronically in the controller. As far as the operator is concerned, these properties are the adjustability of the load dependencies, the tensile or compressive force, and the speed dependency. The response behavior and the power level can likewise be determined in this manner.
Mechanically these properties are obtained in the sensor by means of purposeful design of a bias force around the rest position. The use of defined friction can likewise take account of the aforementioned possibilities.
Electronically, again, the influencing of the system by the operator can take the form of a "modification" of characteristic curves stored in the controller. These characteristic curves represent a relationship between two parameters. In the case under consideration the parameter pairs could be tensile force and speed, tensile force and load, or speed and load.
As a result of the unique drive system and associated steering pole described herein, the present invention creates a unique motion controller based on a feed back controller unit, not merely a controller wherein the motor is engaged in proportion to the deflection of a handle as in many prior motion controller systems. A common problem with earlier motion controllers is motor oscillations wherein the motor accelerates or decelerates alternatingly. The present invention avoids this problem by providing a regulator circuit that accounts for the desired speed of the vehicle as well as for the load placed on the vehicle relative to the proportional force the vehicle operator applies to the control handle or pole.